hardware interface: add copyFrom

Add a copyFrom method to the hardware window interface and empty
implementations of it within the current lpc handlers.

Change-Id: If2ab6a47763387721edd1a0c451ed8c6087eb475
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/lpc_aspeed.hpp b/lpc_aspeed.hpp
index be872ce..c528c3d 100644
--- a/lpc_aspeed.hpp
+++ b/lpc_aspeed.hpp
@@ -22,6 +22,8 @@
     std::pair<std::uint32_t, std::uint32_t>
         mapWindow(std::uint32_t address, std::uint32_t length) override;
 
+    std::vector<std::uint8_t> copyFrom(std::uint32_t length) override;
+
   private:
     std::size_t regionSize;
     const internal::Sys* sys;